This is a wrap up of my off topic? discussion of HF Packet
Radio and is based on lots of input over several years. This
discussion is limited to methods used to transmit digital data over
radio in a 300 Hz bandwidth on 80 through 10 meters.
The first method used by Hams is standard ax25 packets that
worked after we learned to make the data size small. But this made
the standard packet non-data size large compared to the data. But it
worked and we felt it was so slow we should take only personal mail,
no bulletins.
The first method that was used by business is Amtor. Amtor
allows error in the message and it is transmitted 5 bytes at a time.
It works in very bad conditions because of it's small packet size.
Hams played with Amtor and decided their transmitter t/r switches
would never survive this mode!
Some Hams worked up a device they called Clover which is a
computer card you put in your computer and hook your radio to that.
Much was said about how well it worked, but the protocol has been
secret to this day. Clover works with nothing but Clover. If you were
a member of a HF network and the net manager said by next month you
must have purchased Clover or your out of the network! Hams dropped
out in large numbers.
Years passed and Hams in Germany decided to look at HF packet
again and make a system that combined the qualities of Amtor and
Packet to make a system called Pactor. They did a real good job. It
is not clear to me what happened. But it's not important whether
Pactor I followed from Pactor II or the reverse. There exists today
both systems.
Pactor I is code that fits on a 256k e-prom with packet
included! You can buy it from MFJ for $150.00 and it works much
better than straight packet from my experience. The protocol is
complete and defined in the ARRL Handbook, 1996.
Pactor II is more complex code that includes DSP and other
aids to weak signal work. It also can use longer data packets than
Pactor I. I has either 100 or 200 while II goes to 800 bytes. This
makes for better throughput under good conditions.
The true power of Pactor II is none of the above. The single
BEST feature is that it talks fine to Pactor I and Amtor! This means
that two hams, one with more money than the other can still talk
after the expensive system is used. I can not talk too much about how
good this idea is for the current conditions.
AA5BJ has been running a Winlink BBS system using HF Pactor I
in an AEA 232 TNC for 9 years. He scans several frequencies from 80
through 20 meters. His many users are using either AEA 232 or Kam
TNC's and are all over the western USA and Northern Mexico.
Pactor I has been in use for these 9 years and it has worked
fine through the solar minimum we had in the last 5 years. So the
development of Pactor I has made HF packet fun again. Pactor II is an
improvement to a degree unknown at this time. But it talks to Pactor
I and that is very good.
Best wishes
- Karl F. Larsen, [EMAIL PROTECTED] (505) 524-3303 -
